He invested two unknown amount that add to $1200.
Let the amount invested at 9% be x.
Let the amount invested at 3% be y.
The amounts add to $1200.
x + y = 1200 First Equation
The profit from the 9% part is 0.09x.
The profit from the 3% part is 0.03y.
The two profits add to $78.
0.09x + 0.03y = 78 Second Equation
We have two equations in two unknowns, so we can solve this problem as a system of equations.
x + y = 1200
0.09x + 0.03y = 78
Multiply the first equation by -0.09 and add to the second equation.
-0.09x - 0.09y = -108
0.09x + 0.03y = 78
----------------------------
-0.06y = -30
Divide both sides by -0.06
y = 500
Now we substitute 500 into y in the first equation.
x + y = 1200
x + 500 = 1200
x = 700
Answer: The amount invested at 9% is $700
Roland; 20+15+16=51, 51÷3= 17
Roland; 17
We divide 3 because it's the total number of grade she got.
Jetta; 16+19+17=52, 52÷3= 17.1
Jetta; 17.1
So, probably Jetta got better grade than Rolanda
1. 8/9 ÷ 4/9 is done by inverting the divisor (4/9) and then multiplying:
(8/9)(9/4) = 8/4 = 2 (answer)
2. 1/3 ÷ 6 is done similarly: (1/3)(1/6) = 1/18 (answer)
3. 4 ÷ 1/5 = 4 * 5 = 20 (answer)
4. 7 1/2 ÷ 1/4 = (15/2)(4/1) = 30 (answer)
Answer:
i think it's 15 because if you use 5 and you have to do it by 3 it should be 15
